ch in emanations. Uranium, on the
contrary, has none.[37] This body, nevertheless, is the seat of
transformations comparable to those which the study of emanations
reveals in radium; Sir W. Crookes has separated from uranium a matter
which is now called uranium X. This matter is at first much more
active than its parent, but its activity diminishes rapidly, while the
ordinary uranium, which at the time of the separation loses its
activity, regains it by degrees. In the same way, Professors
Rutherford and Soddy have discovered a so-called thorium X to be the
stage through which ordinary thorium has to pass in order to produce
its emanation.[38]

[Footnote 37: Professor Rutherford has lately stated that uranium may
possibly produce an emanation, but that its rate of decay must be too
swift for its presence to be verified (see _Radioactive
Transformations_, p. 161).--ED.]

[Footnote 38: An actinium X was also discovered by Professor Giesel
(_Jahrbuch d. Radioaktivitat_, i. p. 358, 1904). Since the above was
written, another product has been found to intervene between the X
substance and the emanation in the case of actinium and thorium. They
have been named radio-actinium and radio-thorium respectively.--ED.]

It is not possible to give a complete table which should, as it were,
represent the genealogical tree of the various radioactive substances.
Several authors have endeavoured to do so, but in a premature manner;
all the affiliations are not at the present time yet perfectly known,
and it will no doubt be acknowledged some day that identical states
have been described under different names.[39]

[Footnote 39: Such a table is given on p. 169 of Rutherford's
_Radioactive Transformations_.--ED.]

Sec. 4. THE DISAGGREGATION OF MATTER AND ATOMIC ENERGY

In spite of uncertainties which are not yet entirely removed, it
cannot be denied that many experiments render it probable that in
radioactive bodies we find ourselves witnessing veritable
transformations of matter.

Professor Rutherford, Professor Soddy, and several other physicists,
have come to regard these phenomena in the following way. A
radioactive body is composed of atoms which have little stability, and
are able to detach themselves spontaneously from the parent substance,
and at the same time to divide themselves into two essential component
parts, the negative electron and its residue the positive ion. The
first-named constitutes the beta, and the seco